Alkenyl hydroperoxymethanes as polymerization catalysts



Patented Feb. 2, 1954 RQPE 'POLYMERIZAT William B. Reynolds, John E.

Thomas J ROXYMETHANES As ION CATALYSTS 'Wicklatz; and

Kennedy, Bartlesville, Okla, as-

signofs to Phillips Petroleum Company, acor- No Drawin Application August 15,1949,

* .S'eri'alNo. 110,482

fl'Claims. (omen-84.1), I

This invention relates to an improvedprocess for polymerizing unsaturated organic compounds while dispersed inan aqueous emulsion. In one important aspect this invention-relates to the use of fasterrecipesat lowpolymerization temperatures for e-fiecting production of synthetic rubber by emulsion polymerization of conjugated diolefins.

With the increasing interestin low temperature emulsion polymerization, many variations in recipes and procedurehave been developed in. the interest of economy, and efficiencyin addition to the attention given to producing polymeric materials having the desired characteristics. Recipes of the redox type, ,that is, formulations wherein bothoxidizing and reducing C011].- ponents are present, have been widely used. Oxidi-zing components frequently employed include materials of a peroxidic nature, and particularly compounds such as. ;benzoyl peroxide and cumene hydroperoxide. Even though any peroxidic materialmight be expected to function in the capacity of the oxidant in a redox emulsion polymerization system, this is not necessarily the case since in some instances little, if any, polymerization occurs while other cases with different peroxides the reaction takes place at a; satisfactory rate. Some peroxides may function fairly satisfactorily at higher temperatures but are of little value when it isdesired'to carry out polymerizationsat low temperatures, say below We have now discovered that excellent conversion rates are realized when carrying out emulsion polymerization reactions, especially at low-temperatures, using recipes in which the oxidizing component is an valkenyl hydroperoxymethane havingat least six but not more than 30 carbon atomsper molecule. These hydroperoxymethanes, or hyiiroperox'i'des,v can be represented by the. formula wherein R is one of the group consisting of aliphatic, cycloaliphatic; and aromatic radicals; R is hydrogen or an aliphatic, cycloaliphatic, or-an aromatic radical, andR" is an alkenyl radical. Whenan aromatic radical is apart of the molecule, it can have various nonhydrocarbon substituents attached to a nuclear carbon atom, paticularly alkoxy, aryloxy, and halogen. Examples of compounds fromwhichthese hydro- PBIQXidB-S may be pr ar d include E-nhenyLZ- pentene, 5 (4 isopropyl-phenyl) -,2-pntene, '5- phenyl-3-methyl-2-pentene, .4-methyI-2 heXe'ne, 4-phenyl -2 --butene, 5- (4.-inethoxy phenyl) 2- pentene, 5- (4-phenoxyphenyl) 3 methyl=2- pentene, 5-(4-naphthyl) 2rpentene, 5-(4-ch1or'o phenyl) -2-pente ne,. 'various polyisobufylenes,= for polyisobutylene fractionssuchfas produced from juncture of two to seven molecules of .is'obutylen'e, i. e., from diisobutylenet'o heptaisobutylene, or more pure aliphatic olefinssuch as .trica'prylene (9-hexyl-11-methy1 7 heptsaecenen and 2- methyl 5 isoamyl leeicosene, andthedik'e. From the'foregoing, it will be notedthat the number of carbon atoms. in the hydroperoxide molecules set forth in th'e foregoingspecific examples ranges groin 7 (.4-methyl-2-hexene) {to 28 (heptaisobutylen'e). .Advant'ages' .rrom the use of hydroperoxides prepared from such compounds are particularly pronounced sentimeization temperatures below. 10. C., an'd .downto polymerization temperatures. as low .as .30 or 40 C., or lower.

An object of this inventionis to polymerize unsaturated organic co poundswhile dispersed in an aqueous emulsion. 7

Another object of this invention is to pro vide an improved process for the production of synthetic rubber.

A further object of this invention is to shorten the reaction time necessary for the production of synthetic rubber by emulsion polymerization of monomeric materials.

Still another object of this invention isto produce synthetic rubber at a low reaction temperature.

Further objectsand advantages of maintention will become apparent,. to one skilledinth art, from the accompanying. disclosure and dis cussion.

The alkenyl hydroperoxymethane's. used in the practice of this invention can easily be prepared by simple oxidation, with free oxygen, ofthe corresponding parent compound. The com pound to be oxidized is placed ina reactonheated to the desired temperature, and oxygen ,Iii'ntroduced at a controlled ratethroughout thei action period. The mixture is agitated during the reaction which is generally allowed to continue from about thirty minutes to. ten hours or more. The temperature employed is preferablymai'ntained between 50 and C. although in some instances it might be desirable to operate outside this range, that is, at either higher orlower ern- Deratures. At the conclusion of the reaction the; oxidized mixture may be employed as sucngunt is, as a solution of the hydroperoxide in the parent compound, or unreacted material may be removed and the residual material employed.

The major active ingredient resulting from the above described oxidation process is a monohydroperoxide, or mixture of monohydroperoxides. This hydroperoxide formation occurs on tertiary or other active carbon atoms and appears to result from the introduction of two oxygen atoms between a carbon atom and the hydrogen attached thereto. It is generally regarded that oxidation occurs on the carbon atom of the trisubstituted methane, when the molecule contains such a structure. However, when an alkenyl group is present in the molecule with out this structure, a carbon atom, or the carbon atoms, alpha to this group is active and therefore susceptible to such oxidation even though the substituents comprise more than one hydrogen. It is also possible that certain groups present in the molecule, such as phenyl groups, activatethe carbon atoms directly attached thereto making them more susceptible to oxidation.

While in many instances oxidation may occur predominantly on a carbon atom alpha to the alkenyl group, it does not necessarily occur exclusively at this point, since, as already discussed, other carbon atoms in the molecule may also be sufficiently active to undergo reaction. Even though a dihydroperoxide appears to be structurally possible, the usual method of oxidation just outlined appears to produce only the monohydroperoxide. In cases, then, where oxidation can occur on more than one carbon atom in the molecule, the reaction product comprises a mixture monohydroperoxides.

We use the hydroperoxides discussed herein. as oxidants in polymerization recipes at low polymerization temperatures, i. e. from about 10 C., or just above the freezing point of water, to well below the freezing point of water, such as 40" C. or lower, The recipe will also include a reductant compound or composition. In some recipes this will be a single compound, or a mixture of homologous compounds, such as hydrazine, ethylenediamine, diethylene-triamine, aminoethylethanolamine, ethylene-methylethylene-triamine, tetraethylenepentamine, and the like. These com ounds have the general formula RHN CHXCHXNH m(CHXCHX) nNHR where each R contains not more than eight carbon atoms and is of the group consisting of hydrogen, aliphatic, cycloaliphatic, aromatic, olefinic, and cycloolefinic radicals, and each X contains not more than three carbon atoms and is of the group consisting of hydrogen and aliphatic radicals, m is an integer between and 8, inclusive, and n is an integer of the group consisting of 0 and 1 and is 1 when m is greater than 0. Each of the foregoing radicals (other than hydrogen) can be completely hydrocarbon in character, and can be of mixed character when containing six or more carbon atoms, such as aralkyl, alkaryl, and the like, and can also have non-hydrocarbon substituents, some of which will have the effect of making them more water-soluble and less oil(hydrocarbon)-soluble; particularly useful non-hydrocarbon substituents include oxygen in the form of hydroxy and ether compounds, sulfur in similar compounds (i. e. mercapto compounds and thiocthers) and halogen compounds. In such recipes, such a polyamino compound appears to act as a reductant, and no other activating ingredients, such as compounds 01 12 3;-

valent-multivalent metals, or reducing ingredients, such as a reducing sugar, need be present in order to obtain satisfactory and rapid poly merization of the monomeric material, even at subfreezing temperatures. The amount of amine-type compound used to obtain optimum results also is dependent upon other ingredients in the recipe. Preferred results are usually ob tained with between 0.1 to 5 parts by weight,- per parts of monomeric material, of the amine-type compound. In other recipes a composition is used which comprises one compound which is an oxidation catalyst, or activator, and another different compound which is a reductant. The oxidation catalyst is generally selected from a group of materials consisting of compounds ofmetals such as iron, manganese, copper, vanadium, cobalt, etc. In general it is assumed that the metal must be a multivalent metal and in such a condition that it state reversibly. The other ingredient ordinarily present is a reductant, and is usually an organic material such as a reducing sugar or other easily oxidizable polyhydroxy compound. Compounds frequently employed in this capacity are glucose, levulose, sorbose, invert sugar, and the like. The multivalent metal ion of the oxidation catalyst can easily and readily pass from a low valence state to a higher valence state, and vice versa. Sometimes this compound, when present in its lower valence state, can function in the duai role of reductant and oxidation catalyst. One commonly used oxidation catalyst is an iron pyrophosphate, and is separately made up in aqueous solution from a ferrous salt, such as ferrous sulfate, and a pyrophosphate of an alkali metal, such as sodium or potassium.

In efiecting emulsion polymerization of a monomeric material, particularly when a batchtype or semi-batch-type operation is carried out, the reactor is usually first charged with the aqueous medium, which contains the desired emulsifying agent, and the monomeric material is then admixed with agitation of the contents. At the same time a reaction modifier, such as a mercaptan, is also included, usually in solution in at least a part of the monomeric material. An activator solution and an oxidant are separately added to the reaction mixture, and reaction then proceeds. A preferred manner of adding these two constituents is usually to have the activator solution incorporated in the aqueous medium prior to addition of the monomeric material, and to add the oxidant as the last ingredient. Sometimes, however, satisfactory polymerization results can be obtained when this procedure is reversed. It is also sometimes the practice to add portions of one or the other of the activator solutions and oxidant intermittently, or continuously, during the course of the reaction. If the operation is carried out continuously, streams of the various ingredients are admixed in somewhat the same order prior to their final introduction into the polymerization reaction zone.

As previously stated, it is usually desirable that the multivalent metal be present in its lower valence state. With some recipes, it is unnecessary to include an organic reducing agent either inthe activator solution or in the polymerization mixture. However, particularly at temperatures above 0 C., a faster reaction is sometimes obtained with some recipes when a small amount of an organic reducing agent, such as a reducing sugar, is included in the polycan change its valenceenemas meriza'tionrecipe,- and it is frequently more dcsirable to-incorporate this-in'the reaction system by first including itin the activator solution along with the other ingredients. When the multivalent ion is present in its highervalence state, it is usually necessary toin'cl-ude in the activator solution an organic reducing agent. Asa result the multi-valent ion will be partially reduced and a substantial amount of themultr valent ion will be present in its lower valence state when the activator solution is ready "for addition to the polymerization mixture.

'It is usually preferred that the multivalent ion be iron, and the activator solution maybe prepared from any of the readily available soluble iron salts, such as ferrous sulfate, ferric sulfate, ferrous nitrate, and thelike. Apyrophosphate of sodium or potassium is also usually used in preparing the activator-solution. Apparently the ferrous salt andthe pyrophosphate interreact to formsome kind of a complex compound.

The monomeric material polymerized to produce polymers by the process of this invention comprises unsaturated organic compounds which generally contain the characteristic structure CH2=C and, in most cases, have at least one of the disconnected valences attached to an electronegative group, that is, a group which increases the polar character of the molecule such as a chlorine group or an organic group containing a double or triple bond such asvinyl, phenyl, nitrile, carboxy or the like. Included in this class of monomers are the conjugated butadienes or 1,3-butadienes such as (1,3-butadiene), 2,3-dimethyl-l,3-butadiene, isoprene, piperylene, 3.-furyl-l,3-butadiene, 3- methoxy-lB-butadiene and the like; haloprenes, such as chloroprene (2-chlo1-'o l,3-buta diene), bromoprene, methylchloroprene ('2- chloro-3-methyl-l,3-butadiene), and the like; aryl olefins such as styrene, various alkyl styrenes, p-chlorostyrene, p-methoxystyrene, a1pha-meth ylstyrene, vinylnaphthalene and similar derivatives thereof, and the like; acrylic and substituted acrylic acids and their esters, nitriles and amides such as acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, methyl alpha-chloro-acrylate, methacrylate, ethyl methacrylate, butyl methacrylate, methyl ethacrylate, acrylonitrile, methacrylonitrile, methacrylamide and the like, methyl isopropenyl ketone, methyl vinyl ketone, methyl vinyl. ether, vinylet-henyl akyl carbinols, vinyl acetate, vinyl chloride. vinylidene chloride, vinylfurane, vinylcarbazole, vinylacetylene and other. unsaturated hydrocarbons, esters, alcohols, acids, e'thers, etc, of the type described. Such unsaturated compounds may be polymerized alone, inwhich case simple linear polymers are formed, or mixtures cfitwo.

or more of such compounds which are copolymerizable with each other in aqueous emulsion.v may be polymerized to form linear copolymers.

The process of this invention is particularly effective when the monomeric material polymerized is a polymerizable aliphatic conjugated diolefin or a mixture of such conjugated 'diolefin with lesser amounts of onegor more other compounds containing an active CH2:C' group 'which are copolymerizable therewith such as aryl olefins, acrylic and substituted acrylic acids, esters, nitriles and amides, methyl isopropenyl ketone, vinyl chloride, and similar compoundsmentioned hereinabove. In this case the products ofthe polymerization are high molecular weight linearbutadiene polymers and copol-ymers which 'are' rubbery in character and. may be called synthetic rubber. Although, ascan be readily deduced from; the foregoing, "thereis ahost of possible reactants, the -most readily and commercially available monomers at present-are butadiene itself (1,3- butadiene) and styrene. "The invention will, therefore, "be more particularly discussed and exemplified with reference to these typical'reactants. With these specific monomers, it usually preferred to use them together, in relativeratios'oi' butaxdiene to styrene between :85 and '90 z 10 by weight,

It is generally preferred that the emulsion be of an "oil in Water "type, with the ratio of aqueous-mediumto monomeric material between about 0.5 a 1 and about 2:75: 1, in parts by weight. It is frequently desirable to include water-soluble components in the aqueous phase, particularly when the polymerization temperatures" are below freezing. Inorganic salts and alcohols can be so used. Alcohols which are applicable, when operating at lowtemperatures, com-prise water soluble-compoundsof both the monohydric and polyhydric types; and include methyl alcohol, ethylene glycol, glycerine, erythritol, and the like. "The amount oi? alcoholic ingredient used in apolymerization' recipe must "be su'fiicient to prevent'freezingof the aqueous phase and generally ranges from '20 to parts per parts of monomers charged. In most cases the amount of water employed is suificient to make the total quantity of the alcohol-water mixture equal 150 to 2o0parts. In caseswhere it is desired to use a larger quantity of the alcohol-water mixture, say around'250 parts-the amount of alcohol may bein'creased to as much as parts. It is preferred that the alcohol be-such that it is substantially insoluble'in'the non-aqueous phase, and that 90 per cent, or more of the alcohol presont -be in the aqueous phase. A high-boiling alcohol such as glycerine is difiicult to recover from the resulting serum; a low-boiling alcohol such as methanol is easily'removed and frequently preferred. Other low boiling alcohols such as ethanol, however, are frequently too soluble in the liquid monomeric material to permit satisfactory operation. If the resulting latex tends to gel at low reaction temperatures, a larger proportion of aqueous phase should be used. In the "practice ofthe invention suitable means willbe necessary to'establish and maintain an m-erization may be conductedin emulslonandto remove reaction heat to maintain a desired reaction temperature. The polybatches, semicontinuously, or continuously. The total pressure on the reactants is preferably at least as great as the total vapor pressure of the mixture, sothat the initial' reactants will be present in liquid. phase. Usually 50 to 98 per cent of the monomericmaterial is polymerized.

Itzis one: of the outstanding advantages of the use'orthe hydroperoxides. asdisclosed herein, that it is feasible to produce high solids" latices, i. e.. laticesvresulting from the use of an amount terials such as potassium *laurate, potassium .oleate, and "the like, and salts ofrosin acids.

However, other emulsifying agents, such. as non-ionic emulsifying agents, salts of alkyl aromatic sulionic acids, salts of alkyl sulfates, and the like which will produce favorable results under the conditions of the reaction, can also be used in practicing the invention. The amount and kind of emulsifier used to obtain optimum results is somewhat dependent upon the relative amounts of monomeric material; and aqueous phase, the reaction temperature, and the other ingredients of the polymerization mixture. Usually an amount between about 0.3 and parts per 100 parts of monomeric material will be found to be suflicient.

The pH of the aqueous phase may be varied over a rather wide range without producing deleterious efiects on the conversion rate or the properties of the polymer. In general the pH may be within the range of 9.0 to 11.8, with the narrower range of 9.5 to 10.5 being most general ly preferred.

The mercaptans applicable in this invention are usually alkyl mercaptans, and these may be of primary, secondary, or tertiary configurations, and generally range from C3 to C compounds, but may have more or fewer carbon atoms per molecule. Mixtures or blends of mercaptans are also frequently considered desirable and in many cases are preferred to the pure compounds. The amount of mercaptan employed will vary, depending upon the particular compound or blend chosen, the operating temperature, the freezing point depressant employed, and the results desired. In general, the greater modification is obtained when operating at low temperatures and therefore a smaller amount of mercaptan is added to yield a product of a given Mooney value, than is used at higher temperatures. In the case of tertiary mercaptans, such as tertiary C12 mercaptans, blends of tertiary C12, C14, and C15 mercaptans, and the like, satisfactory modification is obtained with 0.05 to 0.3 part mercaptan per 100 parts monomers, but smaller or larger amounts may be employed in some instances. In fact, amounts as large as 2.0 parts per 100 parts of monomers may be used. Thus the amount of mercaptan is adjusted to suit the case at hand.

The amount of alkenyl hydroperoxymethane used to obtain an optimum reaction rate will depend upon the other reaction conditions, and particularly upon the type of polymerization recipe used. The amount is generally expressed in millimols per 100 parts of monomeric material, using in each instance the same units of weight throughout, i. e. when the monomeric material is measured in pounds the alkenyl hydroperoxymethane is measured in millipound mols. The same is true for other ingredients of the polymerization recipe. An optimum rate of polymerization is usually obtained with the amount of alkenyl hydroperoxymethane between 0.1 and 10 millimols per 100 parts by weight of monomeric material. The hydroperoxide can frequently be easily separated from accompanying materials by converting it to a corresponding salt of an alkali metal, which is usually a crystalline material in a pure or concentrated state at atmospheric temperatures, and separating the salt,

This salt can be used as an active form of the hydroperoxide, since it is promptly converted to the hydroperoxide by hydrolysis when the salt is admixed with the aqueous medium of the polymerization reaction mixture.

These hydroperoxide salts can be used, with outstanding results, in recipes incorporating any one of a number of activating or reducing ingredients. When a ferrous pyrophosphate activator is used, it is preferably prepared by admixing a ferrous salt, such as ferrous sulfate, with a pyrophosphate of an alkali metal, such as sodium or potassium, and water and heating this mixture, preferably for the length of time required for maximum activity. A reaction occurs between the salts, as evidenced by the formation of a grayish-green precipitate. When preparing the activator the mixture is generally heated above 50 C., for variable periods depending upon the temperature. For example, if the mixture is boiled. a period of twenty minutes or less is sufficient to produce the desired activity, and the time of boiling may even be as low as 30 seconds. One convenient method of operation involves maintaining the temperature of the activator solution at about 60 C. for a period of from 10 to 30 minutes. Prior to heating the activator mixture the vessel is usually flushed with an inert gas such as nitrogen. In general it is preferred to heat the mixture below the boiling point, say at a temperature around 55 to 75 C.

In cases where the activator is prepared just prior to use, it is generally employed in the form of an aqueous dispersion as described above. However, the solid activator may be isolated and the crystalline product used, and in this form it is preferred in some instances. Subsequent to heating the activator mixture, it is cooled to around room temperature and the solid material separated by centrifugation, filtration, or other suitable means, after which it is dried. Drying may be accomplished in vacuo in the presence of a suitable drying agent, such as calcium chloride, and in an inert atmosphere such as nitrogen. When using this crystalline product in emulsion polymerization reactions, it is generally charged to the reactor just prior to introduction of the butadiene. This crystalline material is believed to be a sodium ferrous pyrophosphate complex, such as might be exemplified by the formula or perhaps NazFePzov. In any event the complex, whatever its composition, is only slightly soluble in water and is one active form of ferrous ion and pyrophosphate which can be successfully used in my invention. It may be incorporated in the polymerization mixture as such, or dissolved in sufficient water to produce solution. Other forms of multivalent metal and pyrophosphate may also be used, so long as there is present in the reacting mixture a soluble form of a multivalent metal, capable of existing in two valence states and present primarily in the lower of two valence states, and a pyrophosphate.

The amounts of activator ingredients are usually expressed in terms of the monomers charged. The multivalent metal should be within the range of 0.10 to 3 millimols per parts by weight of monomers, with 0.2 to 2.5 millimols being generally preferred. The amount of pyrophosphate should be within the range of 0.10 to 5.6 millimols based on 100 parts by weight of monomers; however, the narrower range of 0.2 to 2.5 millimols is more frequently preferred. The mol ratio of ferrous salt to alkali metal pyrophosphate can be between 1:02 and 1:3.5, with a preferred ratio between 1:035

and 1:2.8.

wow

the mixture we tifred."

Pants by we ig Butadiene 72 i Styrene 9-1 9, stqnyimm.

2A blend of tertiary C12, C14, and C16 aliphatic mercape isipz ati 31 1pattswwei lltw The activato; composition" was prepared by heating 'a' mixture of the 'jfei roiis' suli a'te" fiotafi' siu'mpyrophos'phote,"and w tei' at' 60 minutes. The dextrose, potassium hydroxide, and 25 partswater were heated 215 70 6. fo'i 25 minutes andadde'd to the soap Solution, qmmerca yafi dissolved in the "styrene-was the addedj-'ti'1e 5 temperature adjusted to brie" des req iev'el; the butadiene introduced followed by the hydropei' AS will 9?v eyidentlto Oxide, #1 5 fina ly i11 a ivatoy compet W19 difi 'f Polymerization 'was efictl'"9;t5"C.""Thtimeem/amigo dat are resorhdecl' below, together ith the .amomw of. hydrqperoxide employed. PHIBO$$ o oompariwn; :1 70911121301 .r un was made u in cumene' hydron rnaxide, :in van amount Previous y found to be .ont mum for, this recipe:

i "l ,pigenyhg p entene (oxidized to thigh peroxide by char '0 erizingwaiconiugatedidiolefin -the1'pre 11 comprises a reductant, the improvement which comprises effecting said polymerization at a reaction temperature below 10 C. using as said organic hydroperoxide a hydroperoxide resulting from oxidation with free oxygen'of -(4-isopropylphenyl) -2-pentene.

2. In a process for producing a solid polymeric product by polymerizing a conjugated diolefin in aqueous emulsion in the presence of an organic hydroperoxide as an oxidizing constituent of a polymerization catalyst composition which also comprises a reductant, the improvement which comprises efiecting said polymerization at a reaction temperature below C. using as said organic hydroperoxide a hydroperoxide resulting from oxidation with free oxygen of 5-phenyl-2- pentene.

3. In a process for producing a solid polymeric product by polymerizing a conjugated diolefin in aqueous emulsion in the presence of an organic hydroperoxide as an oxidizing constituent of a polymerization catalyst composition which also comprises a reductant, the improvement which comprises efiecting said polymerization at a reaction temperature below 10 C. using as said organic hydroperoxide a hydroperoxide resulting from oxidation with free oxygen of a 5-naphthyl-2- pentene.

4. In a process for producing a solid polymeric product by polymerizing a conjugated diolefin in aqueous emulsion in the presence of an organic hydroperoxide as an oxidizing constituent of a polymerization catalyst composition which also comprises a reductant, the improvement which comprises effecting saidpolymerization at a reaction temperature below 10 C. using as said organic hydroperoxide a hydroperoxide resulting from oxidation with free oxygen of an alkenyl compound containing from seven to twentyeight, inclusive, carbon atoms per molecine.

5. An improved process for producing synthetic rubber, which comprises establishing and maintaining at a polymerization temperature not higher than 10 C. an emulsion of an aqueous phase, a liquid monomeric material comprising a major amount of 1,3-butadiene and a minor amount of styrene, an emulsifying agent, a reaction modifier, an oxidation catalyst comprising a pyrophosphate of a multi-valent metal capable of existing in two valence states, and an alkenyl hydroperoxide containing from seven to twentyeight, inclusive, carbon atoms per molecule.

6. In the polymerization of a monomeric material comprising an organic compound having an active CHz=C group under polymerization conditions while dispersed in an aqueous medium in the presence of a polymerization catalyst composition comprising an oxidant and a reducing composition, the improvement which comprises using as said oxidant an alkenyl hydroperoxide having from seven to twenty-eight, inclusive, carbon atoms per molecule.

'7. The process of claim 6 in which said hydroperoxide is fi-( l-isopropylphenyl)- 1-hydroperoxy-2-pentene.

higher than 10 isting in two valence states, and an alkenyl hydroperoxide containing from seven to twenty-eight, inclusive, carbon atoms per molecule.

10. An improved process for producing synthetic rubber, which comprises establishing and maintaining at a polymerization temperature not C. an emulsion of an aqueous phase, a liquid monomeric material comprising a major amount of 1,3-butadiene and a minor amount of styrene, an emulsifying agent, a reaction modifier, 0.1 to 10 millimols of an alkenyl hydroperoxide having from seven to twenty-eight, inclusive, carbon atoms per molecule, and 0.1 to 5 parts of a polyamino compound having the formula RHN(CHXCHXNH) m(CHXCI-IX) nNHR where each R contains not more than eight carbon atoms and is of the group consisting of hydrogen, aliphatic, cycloaliphatic, aromatic, olefinic, and cycloolefinic radicals, and each X contains not more than three carbon atoms and is of the group consisting of hydrogen and aliphatic radicals, m is an integer between 0 and 8, inclusive, and n is an integer of the group consisting of 0 and 1 and is 1 when m is greater than 0, said amounts being per 100 parts by weight of said monomeric material.

11. An improved process for producing synthetic rubber, which comprises establishing and maintaining at a polymerization temperature not higher than 10 C. an emulsion of an aqueous phase having a pH between 9.0 and 11.8, a liquid hydrocarbon monomeric material comprising a major amount of 1,3-butadiene, an emulsifying agent, a reaction modifier, 0.1 to 10 millimols of 5- (4-isopropylphenyl) -4-hydroperoxy-2-pentene, and 0.1 to 5 parts of tetraethylenepentamine, said amounts being per 100 parts by weight of said monomeric material.

12. An improved emulsion polymerization process, which comprises establishing and maintaining at a polymerization temperature not greater than 10 C. an emulsion comprising an aqueous phase having a pH between 9.0 and 11.8, a liquid hydrocarbon monomeric material comprising a conjugated diene having four to six carbon atoms per molecule, an emulsifying agent, 0.1 to 10 millimols of 5-(4-isopropylphenyl) -4-hydroperoxy-2-pentene, and 0.1 to 5 parts of a polyamino compound having the formula RHN (CHXCHXNH) m(CHXCI-IX) nNHR where each R contains not more than eight carbon atoms and is of the group consisting of hydrogen, aliphatic, cycloaliphatic, aromatic, olefinic, and cycloolefinic radicals, and each X contains not more than three carbon atoms and is of the group consistin of hydrogen and aliphatic radicals, m is an integer between 0 and 8, in-

' elusive, and n is an integer of the group consisting 8. The process of claim 6 in which said hydroperoxide is 5-phenyl-4-hydroperoxy-2-pentene.

9. An improved process for producing synthetic rubber, which comprises establishing and maintaining at a polymerization temperature not higher than 10 C. an emulsion of an aqueous phase, a liquid monomeric material comprising 1,3-butadiene, an emulsifying agent, a reaction modifier, an oxidation catalyst comprising a pyrophosphate of a multi-valent metal capable of exof 0 and 1 and is 1 when m is greater than 0, said amounts being per 100 parts by weight of said monomeric material. v

13. A process for the polymerization of a monomeric material comprising a conjugated diene having from four to six carbon atoms per molecule, which comprises polymerizing said monomeric material while dispersed inan aqueous medium in the presence of a polymerization catalyst composition comprising an oxidant and a reductant in which said oxidant is an alkenyl (alkaryl) -hydroperoxymethane from seven to twentyeight carbon atoms per molecule.

13 r 14 14. The process of claim 13 in which said oxi- FOREIGN PATENTS dant is 5-(4-isopropy1pheny1)-4-hydroperoxy-2- Number Country Date Pentene- ,2 t i a. .26, 1946 LIAM B. REYNOLDS 576 55 Great Br1 a n M r JOHN E. WICKLATZ. 5 OTHER REFERENCES THOMAS J. KENNEDY- Craigee et a1., Chem. Abstracts, vol. 33, 1939,

page 9292. References cited in the me Of this Patent Shearon Jr., Ind. and Eng. Chem, vol. 40,No. 5,

UNITED STATES PATENTS 10 M y 1948, pa s 69- 77- Number Name Date 2,395,523 Vaughn et a1 Feb. 26, 1946 2,569,480 Lorand Oct. 2, 1951 

1. IN A PROCESS FOR PRODUCING A SOLID POLYMERIC PRODUCT BY POLYMERIZING A CONJUGATED DIOLEFIN IN AQUEOUS EMULSION IN THE PRESENCE OF AN ORGANIC HYDROPEROXIDE AS AN OXIDIZING CONSTITUENT OF A POLYMERIZATION CATALYST COMPOSITION WHICH ALSO COMPRISES A REDUCTANT, THE IMPROVEMENT WHICH COMPRISES EFFECTING SAID POLYMERIZATION AT A REACTION TEMPERATURE BELOW 10* C. USING AS SAID ORGANIC HYDROPEROXIDE A HYDROPEROXIDE RESULTING FROM OXIDATION WITH FREE OXYGEN OF 5-(4-ISOPROPYLPHENYL)-2-PENTENE. 